The present invention relates to devices for looking and speaking through a door without opening the door.
A desire has probably existed for as long as there have been doors for a means of identifying and communicating with a caller outside the door without opening it. Numerous devices have long been used for this purpose, including various small hinged or sliding doors mounted on the passage door selectively to obstruct or clear a small opening through the door. Such devices are normally positioned at approximately adult-eye level. Other widely used devices include "fish-eye" lens devices mounted in holes in the door, also at eye level, but such devices do not facilitate oral communication through the door.
Conventional peephole devices typically permit viewing of an area generally opposite the peephole but make it difficult or impossible to see areas close to the door and not directly in front of the peep hole, thereby enabling someone to crouch below or to one side of the peephole against the door or building out of sight of a person looking through the peephole. Furthermore, while such conventional openings permit oral communication through the door, they also typically transmit smoke and heat from a fire and permit transmission of harmful materials by a would-be intruder. "Fish-eye" lens devices provide a wider viewing angle through the door but significantly distort the image and do not provide for oral communication through the door. Conventional "fish-eye" lens devices also frequently transmit heat from one side of the door to the other and may thus reduce the fire rating of a door in which they are mounted.
This is an important concern because many doors on which the use of viewing devices is desirable must be fire rated. Accordingly, use of a viewing device in such doors which reduces the fire rating is not acceptable.
Typical prior art devices for identifying a caller on the other side of a door include the "Attachment For Doors" described in U.S. Pat. No. 1,901,303 to H. F. Keil, the "Door For Panels" described in U.S. Pat. No. 1,799,164 to S. E. Griswold, the "Vandal Resistant Security View Port" described in U.S. Pat. No. 4,571,901 to Morris and Hafner, the "Wide-Angle Spy Glass" described in U.S. Pat. No. 4,116,529 to Yamaguchi and the "Wide Angle Door Viewer" described in U.S. Pat. No. 4,251,127 to Yamaguchi.